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From Bowen Li <bowenl...@gmail.com>
Subject Re: Clarification in TumblingProcessing TimeWindow Documentation
Date Mon, 28 May 2018 06:39:47 GMT
Hi Dhruv,

I can see it's confusing, and it does seem the comment should be improved.
You can find concrete explanation of tumbling window and relative arguments
at
https://ci.apache.org/projects/flink/flink-docs-master/dev/stream/operators/windows.html#tumbling-windows

Feel free to open a PR with better comment.

Thanks,
Bowen



On Sun, May 27, 2018 at 12:43 PM, Dhruv Kumar <gargdhruv36@gmail.com> wrote:

> Hi
>
> I was looking at TumblingProcessingTimeWindows.java
> <https://github.com/apache/flink/blob/master/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/windowing/assigners/TumblingProcessingTimeWindows.java>
and
> was a bit confused with the documentation at the start of this class. It
> says the following:
>
> /**
> * A {@link WindowAssigner} that windows elements into windows based on
> the current
> * system time of the machine the operation is running on. Windows cannot
> overlap.
> *
> * <p>For example, in order to window into windows of 1 minute, every 10
> seconds:
> * <pre> {@code
> * DataStream<Tuple2<String, Integer>> in = ...;
> * KeyedStream<String, Tuple2<String, Integer>> keyed = in.keyBy(...);
> * WindowedStream<Tuple2<String, Integer>, String, TimeWindows> windowed =
> * keyed.window(TumblingProcessingTimeWindows.of(Time.of(1, MINUTES),
> Time.of(10, SECONDS));
> * } </pre>
> */
> It says one can have tumbling windows of 1 minute, every 10 seconds.
> Doesn’t this become a sliding window then? The SlidingProcessTimeWindows.
> java
> <https://github.com/apache/flink/blob/master/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/windowing/assigners/SlidingProcessingTimeWindows.java>
has
> the exact same documentation with just one tiny change (“Windows can
> possibly overlap”). It seems to me that in the above documentation, the
> second Time argument of 10 seconds is for providing the window offset (as
> confirmed here
> <https://github.com/apache/flink/blob/master/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/windowing/assigners/TumblingProcessingTimeWindows.java#L92>)
> and not for starting the tumbling window every 10 seconds.
>
> Thanks
>
>
> --------------------------------------------------
> *Dhruv Kumar*
> PhD Candidate
> Department of Computer Science and Engineering
> University of Minnesota
> www.dhruvkumar.me
>
>

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